COLORADO SPRINGS, Colo. (AP) -- Interior Secretary Ken Salazar is restricting the number of wild horses people can buy from the federal government and promises to prosecute those who sell mustangs for slaughter.

Salazar's announcement comes after reports about Tom Davis, a southern Colorado livestock hauler and horse slaughter proponent who has bought more than 1,700 horses from the Bureau of Land Management since 2009.

Davis' purchases account for 70 percent of BLM wild horse sales since 2009. The Gazette previously reported that the BLM sometimes contacted Davis to see if he'd like to buy more horses.

Davis has told Colorado officials that he shipped some horses out of state, in violation of brand inspection laws. The Alamosa County district attorney is investigating the transfers. But Davis has said he honored contracts promising the animals wouldn't be slaughtered.

Salazar told The Gazette in an interview (http://bit.ly/SOnW5w) that buyers can be prosecuted for falsifying sales applications and for indirectly selling horses to slaughter by reselling to middlemen.

Salazar also said buyers will be limited to five horses every six months. Larger orders must be approved by the BLM's deputy director.

The BLM oversees most of the 35,000 wild horses roaming public lands in the West. They are protected by law from slaughter.

But the agency has struggled with how to manage growing horse herds, which can double naturally within five years if left unchecked. Horses have been injected with drugs and vaccines to slow reproduction and rounded up for adoption, but the BLM currently has more horses in captivity -- more than 45,000 -- than are left roaming the range.

A BLM investigation of Davis' purchases was transferred to the interior department's inspector general in October when it became clear that federal employees could come under scrutiny, Salazar said.

"When I became aware of the magnitude of his purchases and the concerns of illegal activity I asked the BLM to open an investigation of Tom Davis," Salazar said. "If there was impropriety on the part of the BLM or on the part of BLM officials, the investigation will tell us."

Salazar told The Gazette that he has had no relationship with Davis, who like Salazar lives in the San Luis Valley. The larger wild horse sales to Davis began shortly after Salazar became interior secretary.

"I have never done any business with him," Salazar said. "I have never had a conversation with him."